Laravel 4和Eloquent：检索所有记录和所有相关记录

问题描述

我有两个课程：艺术家和乐器。每个艺术家可以播放一个或多个乐器。并且每个乐器可以分配到一个或多个艺术家。所以，我设置了以下课程：

I have two classes: Artist and Instrument. Each Artist can play one or more Instruments. And each Instrument can be assigned to one or more Artists. So, I've set up the following Classes:

Artist.php

public function instruments() {
    return $this->belongsToMany('App\Models\Instrument');
}

Instrument.php

public function artists() {
    return $this->belongsToMany('\App\Models\Artist');
}

那么我有三个数据库表： p>

Then I have three database tables:

artists: id, firstname, lastname, (timestamps)
instruments: id, name
artist_instrument: id, artist_id, instrument_id

我可以成功检索一个艺术家及其相关乐器如下所示：

I'm able to successfully retrieve a one artist and their associated instruments like so:

ArtistController.php

$artist = Artist::find($artist_id);
$instruments = $artist->instruments()->get();
return \View::make('artists')->with('artists', $artists)->with('instruments', $instruments);

我有3个问题：

1. 在我看来，我可以输出 $ artist ，如：

{{ $artist->firstname }}

，我可以通过 $ instruments 来迭代，如：

and I can iterate through $instruments like:

@foreach ($instruments as $instrument)
    <h2>{{ $instrument->name }}</h2>
@endforeach

但是可以迭代 $ artist （我知道只有一个 - 见＃2），每个 $ artist 迭代他们的 $ instruments ？

but is it possible to iterate over $artist (I know there's only one — see #2) and for each $artist iterate over their $instruments?

在我的控制器中，我如何获得所有艺术家及其相关乐器的每一个

In my controller, how would I get all artists and for each of those their associated instruments with the end goal of iterating through them in my view as described in #1.

可以在上述<$ c $的示例中检索特定的列C> ArtistController.php ？我已经尝试过：

Is it possible to only retrieve specific columns in the above example of ArtistController.php? I've tried this:

$artist = Artist::where('id', $artist_id)->get('firstname');
$instruments = $artist->instruments()->get();
return \View::make('artists')->with('artists', $artists)->with('instruments', $instruments);

但是我收到一条错误，说 Collection :: instruments（）未定义。

but I get an error saying Collection::instruments() is undefined.

我假设在我的模型关系中有一些不正确的东西。我也尝试用 Artist.php 定义我的关系，一个 hasMany （我觉得说每个艺术家都有很多乐器 ，但是这给我一个错误，因为它期待一个名为 artists_instruments 的表，它也试图检索该表中不存在的列（如

I'm assuming there's something not right in my model relationships. I've also tried defining my relationship in Artist.php with a hasMany (I think it makes more sense to say "Each Artist hasMany Instruments", but that gives me an error because it's expecting a table named artists_instruments and it's also trying to retrieve columns that wouldn't exists in that table (like name).

推荐答案

您的模型关系很好。

控制器：

$artists = Artist::with('instruments')->get();

return \View::make('artists')->withArtists($artists);

查看：

@foreach ($artists as $artist)

    <h1>{{ $artist->firstname }}</h1>

    @foreach ($artist->instruments as $instrument)

        <h2>{{ $instrument->name }}</h2>

    @endforeach

@endforeach

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